diff --git a/README.md b/README.md
index 061465b..818e4fe 100644
--- a/README.md
+++ b/README.md
@@ -11,8 +11,12 @@ system.
 
 Requires the DJGPP cross-compiler (`i586-pc-msdosdjgpp-gcc`).
 
+The GUI is built as a static library (`lib/libdvx.a`). The demo links
+against it.
+
 ```
-make            # builds bin/demo.exe
+cd dvxdemo
+make            # builds lib/libdvx.a then bin/demo.exe
 make clean      # removes obj/ and bin/
 ```
 
@@ -43,7 +47,9 @@ Supporting files:
 | `dvxCursor.h` | Mouse cursor bitmask data (5 shapes) |
 | `dvxPalette.h` | Default VGA palette for 8-bit mode |
 | `dvxIcon.c` | stb_image implementation unit (BMP/PNG/JPEG/GIF) |
+| `dvxImageWrite.c` | stb_image_write implementation unit (PNG export) |
 | `thirdparty/stb_image.h` | Third-party single-header image loader |
+| `thirdparty/stb_image_write.h` | Third-party single-header image writer |
 
 ## Quick start
 
@@ -151,6 +157,14 @@ Enter the main event loop. Handles mouse movement, button clicks, keyboard
 input, window management, dirty-rectangle compositing, and LFB flush.
 Returns when `dvxQuit()` is called or ESC is pressed.
 
+```c
+bool dvxUpdate(AppContextT *ctx);
+```
+Process one iteration of the event loop: poll input, dispatch events,
+composite dirty regions, and flush. Returns `true` if the GUI is still
+running, `false` when exit has been requested. Use this instead of
+`dvxRun()` when embedding the GUI inside an existing main loop.
+
 ```c
 void dvxShutdown(AppContextT *ctx);
 ```
@@ -451,6 +465,25 @@ WidgetT *wgtTextArea(WidgetT *parent, int32_t maxLen);
 ```
 Multi-line text area (basic).
 
+### Canvas
+
+```c
+WidgetT *wgtCanvas(WidgetT *parent, int32_t w, int32_t h);
+```
+Drawable bitmap canvas with a sunken bevel border. Supports freehand
+drawing with Bresenham-interpolated strokes.
+
+```c
+void    wgtCanvasClear(WidgetT *w, uint32_t color);
+void    wgtCanvasSetPenColor(WidgetT *w, uint32_t color);
+void    wgtCanvasSetPenSize(WidgetT *w, int32_t size);
+int32_t wgtCanvasSave(WidgetT *w, const char *path);
+int32_t wgtCanvasLoad(WidgetT *w, const char *path);
+```
+`wgtCanvasSave` writes the canvas to a PNG file (converting from display
+pixel format to RGB). `wgtCanvasLoad` reads any image format supported by
+stb_image and converts it to display pixel format.
+
 ### Spacing and dividers
 
 ```c
@@ -522,6 +555,13 @@ void wgtDestroy(WidgetT *w);
 ```
 Remove a widget and all its children from the tree and free memory.
 
+```c
+void wgtSetDebugLayout(bool enabled);
+```
+When enabled, draws 1px neon-colored borders around all layout containers
+so their bounds are visible. Each container gets a distinct color derived
+from its pointer.
+
 ### List box operations
 
 ```c
@@ -605,8 +645,10 @@ Windows use a Motif/GEOS-style frame:
 
 Minimized windows appear as 64x64 beveled icons along the bottom of the
 screen. If a window has an icon image set via `dvxSetWindowIcon()`, that
-image is shown; otherwise a nearest-neighbor-scaled snapshot of the window
-content is used. Double-click an icon to restore.
+image is shown; otherwise a nearest-neighbor-scaled thumbnail of the
+window's content buffer is used. Thumbnails are refreshed automatically
+when the window's content changes, with updates staggered across frames
+so only one icon redraws per interval. Double-click an icon to restore.
 
 ---